This invention relates to a computer controlled pattern stitching machine wherein the pattern to be sewn on a piece of cloth may be reduced or enlarged in scale.
A conventional pattern stitching machine having a scaling mechanism according to the prior art will be described in connection with FIG. 1 of the drawings, which shows a cloth feeding device provided with such a conventional scaling mechanism. A pattern cam 10 rotating in the direction of arrow A in synchronization with the rotation of a shaft arm is pivotally mounted on a cam shaft (not shown). A pattern arm 14 has a follower roller 12 at one end which rides in a cam groove 10a cut into the surface of the pattern cam 10 to carry out a predetermined pattern stitching operation. As the pattern cam 10 is rotated the pattern arm 14 swings inwardly and outwardly as indicated by arrow B through the engagement of the roller 12 with the cam groove 10a.
A scaling mechanism 16 is provided at the other end of the pattern arm 14, and includes a link 18 coupled to the pattern arm which swings back and forth as shown by arrow C in association with the arm 14, and a link 22 slidably engaged through a connecting screw 20 with a groove 18a cut in the link 18, the link 22 thus swinging back and forth as shown by arrow D in association with the movement of the link 18. The connecting screw 20 is initially slid along the groove 18a to a desired position corresponding to a predetermined scaling factor, and is then secured in such position whereafter the links 18 and 22 are pivotally coupled to each other by the screw 20.
A cloth holding device 26 is coupled to one end of the scaling mechanism 16 through an X pattern shaft schematically shown at 24. As the link 22 swings the clothing holding device 26 is reciprocated along the X-axis by the shaft 24 as shown by arrow E, and at the same time a needle bar mechanism (not shown) is reciprocated vertically in the usual manner to stitch a predetermined pattern.
The above described cloth feeding device transmits only motion in the X-axis direction to the holding device 26. The Y-axis motion is transmitted to the holding device by a similar mechanism, not shown for the sake of simplicity.
As will be clear from the above description, the desired pattern scaling factor is provided through the slidable adjustment of the connecting screw 20 in the groove 18a of link 18. Thus, if the screw 20 is moved to the left in FIG. 1 the scale of the pattern being stitched is enlarged, and vice versa. The adjustment of the connecting screw 20 in this prior art mechanical pattern scaling mechanism is both troublesome and time consuming, and the accuracy of the adjustment tends to become seriously degraded with time owing to the wear of the comparatively intricate moving components.